How to split string contains separator in javascript?

I have string like as “1 + 2 - 3 + 10“. I want split it to "1", "+2", "-3", "+10".

Here is my code.

var expression = "1 + 2 - 3 + 10";
expression = expression.replace(/s+/g, '');
let fields = expression.split(/([+-]d+)/g);
console.log(fields);

But result is

["1", "+2", "", "-3", "", "+10", ""]

How can I make result ["1", "+2", "-3", "+10"]?

Answer

Your regular expression takes a group

/([+-]d+)/
 ^       ^  group 

which is included in the result set.

as result you get for each following iteration two parts, the part previous from the group and the group itself.

"1"    first find
"+2"   group as separator for splitting, included to result set
 ""    second find, empty because of the found next separator
"-3"   second separator/group
""     third part without separator
"+10"  third separator
""     rest part between separator and end of string

You could split with a positive lookahead of an operator.

const
    string = '1 + 2 - 3 + 10',
    result = string.replace(/s+/g, '').split(/(?=[+-])/);

console.log(result);